National Party leader Simon Bridges says police have worked out the identity of the person who claimed to leak his expense details.
Last week, Mr Bridges received a "dark and concerning" text from an unknown number claiming to be a National MP. They said they had leaked because Mr Bridges was "arrogant" and they disliked his leadership.
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They also said they had a "long and serious mental health issue" and pleaded for the investigation into their actions to be dropped.
Speaking to media on Friday, Mr Bridges said the person made it "very clear" in their text message there would be significant harm to them if the investigation by speaker Trevor Mallard continued.
"It was my very clear view there would be significant harm to them if the investigation proceeded. It was a dark and concerning text message," he says.
"I was very worried about it. I spoke to senior colleagues and then replied, saying my utmost concern was for the welfare of the person."
He then went to police and shared the texts out of concern for the person's safety.
"On Friday I informed the police with my clear concern being for the mental health and wellbeing of the individual," he says.
"On Sunday evening police contacted me. They knew and had worked out the identity of the person concerned. They made clear the person was getting the help they needed."
Police kept the name confidential and Mr Bridges wants the investigation to continue, despite the texter's plea.
Mr Bridges said he has received expert mental health advice, and "at no time did police tell me that the investigation should not proceed".
Police say the information they received required an "immediate response".
"Steps were taken as they are for any matter reported to police where there are immediate concerns for the welfare of an individual," a spokesperson says.
"The National Party was advised that Police would not disclose the individual's identity for privacy reasons. Police have dealt with this matter entirely from a mental health perspective."
Mr Bridges said there are a "range of credible scenarios" for who the person is, including an MP, a staffer, a member of Parliamentary Services or a person in the "wider system".
"I can't think who it is... I feel strong support. Whether it's a National MP... I hope we can find out," he says.
"What's also really important is the integrity of the Parliamentary system. It's not about the National Party, the Opposition, it's about everyone having confidence in the integrity of the Parliamentary system."
And he hopes the person continues to get the mental health support they need.
"I'm not a cold-hearted person," he says. "We're not cold-hearted people. We want to help in National."